Position sensors that detect the rotational movement of an object such as a camshaft or crankshaft are known in the art. The sensors can comprise magnetic field sensors that can be used to infer a position of the rotating object based on a measured magnetic field detected by the sensors. The magnetic field sensors can utilize various types of sensor elements, including Hall effect sensor elements (e.g., ordinary Hall plates and/or vertical Hall effect devices), magnetoresitive (MR) sensor elements, such as anistotropic MR (AMR), giant MR (GMR), tunneling MR (TMR), colossal MR (CMR), or others.
Conventional magnetic field position sensors also can be twist-insensitive or twist-sensitive sensors. Twist-insensitive sensors generally are magnetic field sensors that are sensitive to magnetic field components in an air-gap direction (e.g., z-direction, or the direction defining the distance between a sensor element and the target), and in which the sensor output should not change in response to a rotation of the sensor by an arbitrary angle around the z-axis (i.e., air-gap axis). On the other hand, twist-sensitive sensors are magnetic field sensors that are sensitive to magnetic field components in a direction of movement (e.g., x-direction) of an object, such as a soft magnetic target device.
Conventional position sensors suffer from several disadvantages. Generally, they are not robust with respect to background magnetic interference. Additionally, they can have difficulty discriminating a bias magnetic field from the field modulation to be sensed. Importantly, conventional position sensors also can be challenged by magnetic threshold definition, or precisely when the signal should switch between low and high (e.g., in a transition from gap to tooth when a tooth-wheel is used), or vice-versa, as the tooth-wheel rotates. Calibration techniques are known and can be used to improve magnetic threshold definition, but they can be delayed (i.e., not operational immediately from power-on).